High-molecular-weight polymeric material comprising diketopyrrolopyrrole pigments

ABSTRACT

The present invention relates to high-molecular-weight polymeric material comprising at least one diketopyrrolopyrrole pigment of formula (1) wherein R 1 , is hydrogen, chlorine, methyl, methoxy, CF 3  or CN, R 2  is hydrogen, chlorine, methyl, methoxy, CF 3  or CN, A is hydrogen, chlorine, methyl, mehtoxy, CF 3 , CN, unsubstituted or substituted phenyl or a radical of formula (2), (2a) or (2b), wherein R 5  is hydrogen, chlorine, methyl, methoxy, nitro, CF 3  or CN and R 6  is hydrogen, chlorine, methyl, methoxy, nitro, CF 3  or CN, or R 5  and R 6  together with the phenyl ring to which they are bonded form an aryl or a heteroaryl and A 1  is a radical of formula (2), (2a) or (2b), to the preparation of that material and to the use thereof in colour filters, and to novel diketopyrrolopyrrole pigments.

The invention relates to a high-molecular-weight organic material thepigmentation of which consists of extremely fine particles, thepigmentation comprising at least one pigment from the class ofdiketopyrrolopyrrole compounds, and to novel diketopyrrolopyrrolepigments. That material is preferably employed in the form of thinlayers that are built up in one or more layers in the form of patternson a transparent substrate and can be used as optical colour filters.

Colour filters are an extremely exacting technology which also demandsvery high standards of the colouring agents. Three pigmentationprocesses that are fundamentally different in principle are known forthe production of colour filters. A number of variants thereof isdescribed in Displays 14/2, 115 (1993).

For example, it is possible to use colorants that can be completelydissolved in a binder, in a conventional solvent or in a solution of thebinder in a conventional solvent. According to JP-A-08/44050, a colourstrength of ≧2.8 is possible for a film thickness of ≦1.25 μm.Disadvantages of the colorants are their inadequate thermal stabilityand fastness to light.

On the other hand, it is also possible to use dispersions of pigmentsthat are completely insoluble in a binder or in a conventional solventor are soluble therein only in an extremely low concentration. A numberof variants of that method has been disclosed in Journal of the SID 1/3,341-346 (1993) and at the IDW'95 (Contribution CF-3, pages 57 to 60 ofthe printed version). In order to obtain the necessary particle finenesscorresponding to a very high specific surface, prolonged grinding withthe application of high friction energy is required. According toContribution CF-5 at the IDW'95 (pages 65 to 68 of the printed version),the particle size is to be very fine, 0.1 μm maximum.

A third alternative consists of chemically modifying pigments in such amanner that they are completely soluble in a ready-for-use mixture of abinder and a conventional solvent. After coating and the usual furtherprocessing, the pigment can be regenerated, the pigment precursorshaving to undergo a reaction that obviously requires a high activationenergy.

The formulation of extremely fine pigments in such a manner that thecoloristic properties conforming to exact standards are obtained istherefore extremely difficult by the previously known methods.

The production of colour filters by sequential application of a red,blue and green colouring agent to a suitable substrate, such as, forexample, amorphous silicon, is also described in GB-A-2 182 165. Thecolour filters can be coated, for example, using inks, especiallyprinting inks, comprising the diketopyrrolopyrrole pigments usedaccording to the invention, or can be produced, for example, by mixingthe diketopyrrolopyrrole pigments used according to the invention withchemically, thermally or photochemically structurablehigh-molecular-weight material. The further production can be carriedout, for example, analogously to EP-A-654 711 by application to asubstrate, e.g. glass used for LCD, subsequent photo-structuring anddevelopment. Other documents that describe the production of colourfilters are U.S. Pat. No. 5,624,467 and WO 98/45756.

For the production of colour filters pigments of thediketopyrrolopyrrole class, so-called DPP pigments, have also been usedfor some time.

For example, EP-A-704 497 describes mixed crystals and solid solutionsof symmetrical diketopyrrolopyrroles that are isomorphous with thecrystal structure of an asymmetrical diketopyrrolopyrrole and can beused for pigmenting high-molecular-weight organic substances.

EP-A-654 506 discloses synergistic pigment mixtures that can be used inplastics materials, surface coatings or printing inks, it being possiblealso for pigments of the diketopyrrolopyrrole class inter alia to beused.

EP-A-340 968 discloses an electrolytic process for the production ofpigmented thin layers, diketopyrrolopyrrole Red 254 (C.I. Pigment Red254) inter alia being used as pigment.

The alternative method, by which pigments are chemically modified insuch a manner that they are completely soluble in a ready-for-usemixture of a binder and a conventional solvent and are regenerated aftercoating and the usual further processing, is described, for example, inEP-A-654 711 and EP-A-742 255, diketopyrrolopyrrole Red 255 (C.I.Pigment Red 255) inter alia being used as pigment.

The DPP pigments used for the production of colour filters up to thepresent time, however, have the disadvantage inter alia that they do notblock out a specific blue-tinged red shade with high transparency.

There is therefore a need for new DPP pigments that have such ablue-tinged red shade in terms of their hue, are coloristically pure andare distinguished by having a high transparency.

Surprisingly, it has now been found that the DPP pigments used accordingto the invention largely satisfy the above-mentioned criteria.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 is a UV/Vis Spectrum of the pigment of formula 100 prepared inExample 1b.

The present invention accordingly relates to a high-molecular-weightpolymeric material comprising at least one diketopyrrolopyrrole pigment(DPP pigment) of formula

wherein

-   R₁ is hydrogen, chlorine, methyl, methoxy, CF₃ or CN,-   R₂ is hydrogen, chlorine, methyl, methoxy, CF₃ or CN,-   A is hydrogen, chlorine, methyl, methoxy, CF₃, CN, unsubstituted or    substituted phenyl or a radical of formula

wherein

-   R₅ is hydrogen, chlorine, methyl, methoxy, nitro, CF₃ or CN and-   R₆ is hydrogen, chlorine, methyl, methoxy, nitro, CF₃ or CN, or-   R₅ and R₆ together with the phenyl ring to which they are bonded    form an aryl or a heteroaryl ring and-   A₁ is a radical of formula

wherein

-   R₅ is hydrogen, chlorine, methyl, methoxy, nitro, CF₃ or CN and-   R₆ is hydrogen, chlorine, methyl, methoxy, nitro, CF₃ or ON, or-   R₅ and R₆ together with the phenyl ring to which they are bonded    form an aryl or a heteroaryl ring.

Preference is given to a high-molecular-weight polymeric materialcomprising at least one diketopyrrolopyrrole pigment (DPP pigment) offormula

wherein

-   R₁ is hydrogen, chlorine, methyl, methoxy, CF₃ or CN,-   R₂ is hydrogen, chlorine, methyl, methoxy, CF₃ or CN,-   R₃ is hydrogen, chlorine, methyl, methoxy and-   R₄ is hydrogen, chlorine, methyl, methoxy or-   R₃ and R₄ together with the phenyl ring to which they are bonded    form a heteroaryl, and-   A is hydrogen, chlorine, methyl, methoxy, CF₃, CN, unsubstituted or    substituted phenyl or a radical of formula

wherein

-   R₅ is hydrogen, chlorine, methyl, methoxy, nitro, CF₃ or CN and-   R₆ is hydrogen, chlorine, methyl, methoxy, nitro, CF₃ or CN.-   R₁ is preferably hydrogen, chlorine or methyl, especially hydrogen    or chlorine.-   R₂ is preferably hydrogen, chlorine or methyl, especially hydrogen    or chlorine.-   R₃ is preferably hydrogen, methyl or methoxy.-   R₄ is preferably hydrogen, methyl or methoxy.-   R₅ is preferably hydrogen, methyl or methoxy.-   R₆ is preferably hydrogen, methyl or methoxy.

A is preferably hydrogen, chlorine, methyl, phenyl or a radical offormula (2).

The present invention further relates to diketopyrrolopyrrole pigmentsof formula (1)

wherein

-   R₁ is hydrogen, chlorine, methyl, methoxy, CF₃ or CN,-   R₂ is hydrogen, chlorine, methyl, methoxy, CF₃ or CN,-   A is hydrogen, chlorine, methyl, methoxy, CF₃, CN, unsubstituted or    substituted phenyl or a radical of formula

wherein

-   R₅ is hydrogen, chlorine, methyl, methoxy, nitro, CF₃ or CN and-   R₆ is hydrogen, chlorine, methyl, methoxy, nitro, CF₃ or CN, or-   R₅ and R₆ together with the phenyl ring to which they are bonded    form an aryl or a heteroaryl ring and-   A₁ is a radical of formula

wherein

-   R₅ is hydrogen, chlorine, methyl, methoxy, nitro, CF₃ or CN and-   R₆ is hydrogen, chlorine, methyl, methoxy, nitro, CF₃ or CN, or-   R₅ and R₆ together with the phenyl ring to which they are bonded    form an aryl or a heteroaryl ring, with the proviso that, when both    of A and A₁ are a radical of formula (2), R₅ cannot be hydrogen and-   R₆ cannot be methyl bonded in the 4-position.

Preference is given to diketopyrrolopyrrole pigments of formula

wherein

-   R₁ is hydrogen, chlorine, methyl, methoxy, CF₃ or CN,-   R₂ is hydrogen, chlorine, methyl, methoxy, CF₃ or CN,-   R₃ is hydrogen, chlorine, methyl, methoxy and-   R₄ is hydrogen, chlorine, methyl, methoxy or-   R₃ and R₄ together with the phenyl ring to which they are bonded    form a heteroaryl, and-   A is hydrogen, chlorine, methyl, methoxy, CF₃, CN, unsubstituted or    substituted phenyl or a radical of formula

wherein

-   R₅ is hydrogen, chlorine, methyl, methoxy, nitro, CF₃ or CN and-   R₆ is hydrogen, chlorine, methyl, methoxy, nitro, CF₃ or CN, with    the proviso that, when A is a radical of formula (2), R₃ and R₅    cannot be hydrogen and R₄ and R₅ cannot be methyl bonded in the    4-position.

The diketopyrrolopyrrole pigments of formula (1) according to theinvention are prepared analogously to generally known preparationmethods for diketopyrrolopyrroles as described in U.S. Pat. No.4,579,949, by first reacting, for example, a nitrile of formula

wherein R₁ is as defined above and X is a leaving group, with a compoundof formula

wherein R₅ and R₆ are as defined above, and then with a succinic aciddiester, or by oxidising a compound of formula

resulting from the compounds of formulae (50) and (51) to a compound offormula

or to a compound of formula

and then reacting with a succinic acid diester,or by first reacting a mixture of two nitrites of formulae

wherein R₁ and R₂ are as defined above and X is a leaving group, with acompound of formula

wherein R₅ and R₆ are as defined above, and then reacting with asuccinic acid diester, or by oxidising a mixture of compounds offormulae

resulting from the compounds of formulae (50), (52) and (51) to amixture of compounds of formulae

or to a mixture of compounds of formulae

and then reacting with a succinic acid diester.

X as a leaving group is to be understood as being, for example, afluorine, chlorine, bromine, iodine, nitro or sulfo group.

The two nitriles-of formulae (50) and (52) can be used in a molar ratioof from 99:1 to 1:99, and advantageously in a molar ratio of 1:1, toeach other.

The nitrites of formulae (50) and (52) and the compounds of formulae(51), (51a), (51b), (51bb), (51c), (51cc), (51d) and (51dd) are known orcan be prepared analogously to generally known processes.

The diketopyrrolopyrrole pigments of formula (1) according to theinvention might also be prepared analogously to a method described inEP-A-1 073 659.

According to the invention, preference is given to diketopyrrolopyrrolepigments of formula (1) that have a transmission at 570-580 nm of lessthan 5% and a transmission at 615 nm of at least 80% and preferably 85%.

High-molecular-weight organic materials are understood as being thosehaving a molecular weight of approximately from 10³ to 10⁷ g/mol.

Special preference is given to high-molecular-weight organic materialbased on acrylates or methacrylates.

The pigmented high-molecular-weight organic material according to theinvention is coated onto a transparent substrate as a layer having athickness of preferably ≦20 μm, especially ≦10 μm, more especially ≦5μm. In the case of a plurality of layers, each individual layer ispreferably ≦5 μm in thickness, especially ≦2 μm. The substratepreferably has at from 400 to 700 nm a transparency of ≧90% throughout,especially ≧95%, more especially ≧98% throughout. Preferably, both thesubstrate and all layers are flat, the surface roughness thereof beingespecially ≦0.1 μm. Glass or polycarbonate film, for example, can beused as flat substrates.

Other preferred properties of colour filters are known to the personskilled in the art and are to be found, for example, in the relevantliterature or in the publications already mentioned.

Preference is given to a transparent substrate to which a red, a blueand a green layer have been applied in any desired sequence, a red DPPpigment of formula (1) according to the invention being used togetherwith known blue and green compounds.

The treatment that is subsequently carried out where applicable will beone of the conventional, known after-treatments, such as, for example,thermal curing or treatment with a developing bath.

The pigmented high-molecular-weight organic materials according to theinvention have a high colour strength, brilliance and transparency. Theyare eminently suitable for the production of red colour filters forvisible light in the range of from 400 to 700 nm.

The invention further relates to a method of modifying the spectrum of avisible light beam by selective absorption of a portion of the radiationby means of a coloured medium, which method comprises using as thecoloured medium a pigmented high-molecular-weight polymeric materialaccording to the invention applied to a transparent substrate.

The present invention further relates accordingly to the colour filtersproduced with the high-molecular-weight polymeric material comprising atleast one diketopyrrolopyrrole pigment.

The colour filters according to the invention can be used with excellentresults in liquid crystal displays, plasma displays orelectro-luminescent displays. The latter may be, for example, active(twistnematic) or passive (supertwistnematic) ferroelectric displays orlight-emitting diodes.

The following Examples serve to illustrate the invention. Unless statedotherwise, parts therein are parts by weight and percentages arepercentages by weight. Temperatures are given in degrees Celsius. Therelationship between parts by weight and parts by volume is the same asthat between grams and cubic centimetres:

EXAMPLE 1a

A mixture consisting of 68.8 g (0.5 mol) of 4-chlorobenzonitrile, 103.7g (0.75 mol) of potassium carbonate and 500 ml of dimethylacetamide isplaced in a laboratory reaction flask. 52.2 g (0.51 mol) of thiophenolare added dropwise to that mixture over a period of 1.5 hours at roomtemperature and with stirring. The reaction mixture is then stirred at110° C. for 14 hours and is then cooled to room temperature. The cooledreaction mixture is discharged into a two-component mixture consistingof 1000 ml of diethyl ether and 800 ml of water, and the organic phaseis separated off and then washed four times with 500 ml of water eachtime and once with 300 ml of a saturated sodium chloride solution. Afterdrying over magnesium sulfate, the solvent is removed in vacuo. 86.4 g(82% of the theoretical yield) of a compound of formula

are obtained.

The compounds listed in Table 1 can be prepared analogously to theprocess described in Example 1a)

TABLE 1 starting material 1 starting material 2 compound 2-naphthylthiol4-chlorobenzonitrile

4-methylthiophenol 4-chlorobenzonitrile

4-methoxythiophenol 4-chlorobenzonitrile

4-nitrothiophenol 4-chlorobenzonitrile

thiophenol 3,4-dichlorobenzonitrile

4-methylthiophenol 3,4-dichlorobenzonitrile

EXAMPLE 1b:

In a laboratory reaction flask, 10.35 g (0.45 mol) of sodium and 100 mlof tert-amyl alcohol are heated under reflux for 12 hours at atemperature of from 110 to 115° C. To the resulting clear solution thereis added dropwise at 105° C., with stirring, over a period of 3 hours, amixture consisting of 42.3 g (0.2 mol) of the compound of formula (53)from Example 1a, 24.8 ml (0.12 mol) of succinic acid diisopropyl esterand 50 ml of tert-amyl alcohol.

A further 4.14 ml (0.02 mol) of succinic acid diisopropyl ester is thenadded dropwise over a period of 1 hour. When the addition is complete,the resulting dark-red suspension is maintained at 105° C., withstirring, for a further 30 minutes and is then cooled to 15° C. Thesuspension is then discharged into a mixture consisting of 500 ml ofwater, 100 ml of methanol and 36.8 g (0.6 mol) of acetic acid at atemperature below −5° C. and is stirred at that temperature for 12 hoursto complete the reaction.

The finely particulate pigment suspension obtained in that manner isfiltered off and washed with 1500 ml of methanol and 2000 ml of water.Drying in vacuo at 80° C. yields 41.1 g (81% of the theoretical yield)of a red pulverulent compound of formula

having the spectrum indicated in FIG. 1, which in PVC results in atransparent blue-tinged red coloration.

The diketopyrrolopyrrole pigments listed in Table 2 can be preparedanalogously to the process described in Example 1b)

TABLE 2 starting material diketopyrrolopyrrole pigment shade

blue-tinged red

blue-tinged red

blue-tinged red

blue-tinged red

blue-tinged red

EXAMPLE 2

A mixture consisting of 34.38 g (0.25 mol) of 4-chlorobenzonitrile,51.22 g (0.31 mol) of anhydrous sodium benzenesulfinate and 3500 ml ofN,N-dimethylacetamide is placed in a laboratory reaction flask andheated at a temperature of from 140 to 152° C. for 5 hours and stirredat 120° C. for 15 hours to complete the reaction. The resulting yellowsuspension is cooled and the solvent is removed in vacuo in a rotaryevaporator. The resulting solid residue is taken up in 1.5 litres ofwater, filtered and washed with 1.4 litres of water. Drying in vacuoyields 57.9 g (95% of the theoretical yield) of a pale-yellow compoundof formula

EXAMPLE 3

The procedure is analogous to Example 2 except that 56.8 g of anhydroussodium 4-toluenesulfinate are used instead of the sodiumbenzenesulfinate. 59.2 g (92% of the theoretical yield) of a pale-yellowcompound of formula

are obtained.

EXAMPLE 4

In a laboratory reaction flask, 2.58 g (0.112 mol) of sodium and 60 mlof tert-amyl alcohol are heated under reflux for 12 hours at atemperature of from 110 to 115° C. To the resulting clear solution thereis added dropwise at 105° C., with stirring, over a period of 3 hours amixture consisting of 12.15 g (0.05 mol) of the compound of formula (54)from Example 2, 9.04 g (0.07 mol) of succinic acid diisopropyl ester and60 ml of tert-amyl alcohol.

When the addition is complete, the resulting dark-red suspension ismaintained at 105° C., with stirring, for a further 30 minutes and isthen cooled to room temperature. The suspension is then discharged intoa mixture consisting of 250 ml of water, 50 ml of methanol and 9.0 g(0.15 mol) of acetic acid at a temperature below 30° C. and is stirredat room temperature for 15 hours to complete the reaction.

The finely particulate pigment suspension obtained in that manner isfiltered off and washed with 1000 ml of methanol and 500 ml of water.After drying in vacuo at 90° C., 12.9 g (91% of the theoretical yield)of a red pulverulent compound of formula

are obtained, which in PVC results in a transparent blue-tinged redcoloration.

EXAMPLE 5

The procedure is analogous to Example 4 except that, instead of compound(54), an equimolar amount of the compound of formula (55) is used. A redpulverulent compound of formula

is obtained in a yield of 95%, which in PVC results in a transparentblue-tinged red coloration.

EXAMPLE 6

Production of a red colour filter 8.35 g of the DPP pigment from Example1b, 0.42 g of a quinacridone mixture comprising the compound of formula

0.42 g of a sulfonated diketopyrrolopyrrole prepared according toExample 1 a+b of GB-A-2 238 550, 0.35 g of Solsperse® 22'000 (Avecia),1.75 g of Solsperse® 24'000 (Avecia) and 40.0 g of propylene glycolmonomethyl ether acetate (MPA, CAS Reg. No 108-65-6) are loaded into a180 ml glass vessel containing 235 g of zircon ceramic balls and stirredat 20° C., using a Dispermat, at 1000 rev/min for 10 minutes and at 3000rev/min for 180 minutes. After the addition of 14.3 g of an acrylatepolymer binder (40% solution in MPA), the mixture is further stirred at3000 rev/min for 30 minutes at room temperature. After removal of theballs, the dispersion is diluted with the same amount by weight of MPA.

On a spin-coating apparatus, a glass substrate (Corning Type 1737-F) iscoated with that dispersion and spun at 1000 rev/min for 30 seconds.Drying of the layer is carried out at 100° C. for 2 minutes and at 200°C. for 5 minutes on a heating plate. The layer thickness obtained isbetween 0.4 and 0.5 μm.

EXAMPLE 7

Production of a red colour filter 8.35 g of the DPP pigment from Example1b, 0.42 g of a dihydroquinacridone compound of formula

0.42 g of a sulfonated diketopyrrolopyrrole prepared according toExample 1a+b of GB-A-2 238 550, 0.35 g of Solsperse® 22'000 (Avecia),1.75 g of Solsperse® 24'000 (Avecia) and 40.0 g of propylene glycolmonomethyl ether acetate (MPA, CAS Reg. No 108-65-6) are loaded into a180 ml glass vessel containing 235 g of zircon ceramic balls and stirredat 20° C., using a Dispermat, at 1000 rev/min for 10 minutes and at 3000rev/min for 180 minutes. After the addition of 14.3 g of an acrylatepolymer binder (40% solution in MPA), the mixture is further stirred at3000 rev/min for 30 minutes at room temperature. After removal of theballs, the dispersion is diluted with the same amount by weight of MPA.

On a spin-coating apparatus, a glass substrate (Corning Type 1737-F) iscoated with that dispersion and spun at 1000 rev/min for 30 seconds.Drying of the layer is carried out at 100° C. for 2 minutes and at 200°C. for 5 minutes on a heating plate. The layer thickness obtained isbetween 0.4 and 0.5 μm.

The colour filters produced with the diketopyrrolopyrrole pigments usedaccording to the invention are distinguished by a high transmission ofthe colour dots.

1. A high-molecular-weight polymeric material comprising at least one diketopyrrolopyrrole pigment (DPP pigment), which pigment has a particle size of less than or equal to 0.1 μm, has a transmission at 570-580 nm of less than 5% and a transmission at 615 nm of at least 80%, and consists of compounds of formula

wherein R₁ is hydrogen, chlorine, methyl, methoxy, CF₃ or CN, R₂ is hydrogen, chlorine, methyl, methoxy, CF₃ or CN, A is hydrogen, chlorine, methyl, methoxy, CF₃, CN, unsubstituted or substituted phenyl or a radical of formula

wherein R₅ is hydrogen, chlorine, methyl, methoxy, nitro, CF₃ or CN and R₆ is hydrogen, chlorine, methyl, methoxy, nitro, CF₃ or CN, or R₅ and R₆ together with the phenyl ring to which they are bonded form an aryl or a heteroaryl ring and A₁ is a radical of formula

wherein R₅ is hydrogen, chlorine, methyl, methoxy, nitro, CF₃ or CN and R₆ is hydrogen, chlorine, methyl, methoxy, nitro, CF₃ or CN, or R₅ and R₆ together with the phenyl ring to which they are bonded form an aryl or a heteroaryl ring.
 2. A diketopyrrolopyrrole pigment, which pigment has a particle size of less than or equal to 0.1 μm, has a transmission at 570-580 nm of less than 5% and a transmission at 615 nm of at least 80%, and consists of compounds of formula

wherein R₁ is hydrogen, chlorine, methyl, methoxy, CF₃ or CN, R₂ is hydrogen, chlorine, methyl, methoxy, CF₃ or CN, A is hydrogen, chlorine, methyl, methoxy, CF₃, CN, unsubstituted or substituted phenyl or a radical of formula

wherein R₅ is hydrogen, chlorine, methyl, methoxy, nitro, CF₃ or CN and R₆ is hydrogen, chlorine, methyl, methoxy, nitro, CF₃ or CN, or R₅ and R₆ together with the phenyl ring to which they are bonded form an aryl or a heteroaryl ring and A₁ is a radical of formula

wherein R₅ is hydrogen, chlorine, methyl, methoxy, nitro, CF₃ or CN and R₆ is hydrogen, chlorine, methyl, methoxy, nitro, CF₃ or CN, or R₅ and R₆ together with the phenyl ring to which they are bonded form an aryl or a heteroaryl ring, with the proviso that, when both of A and A₁ are a radical of formula (2), R₅ cannot be hydrogen and R₆ cannot be methyl bonded in the 4-position.
 3. A diketopyrrolopyrrole pigment according to claim 2 of formula

wherein R₁ is hydrogen, chlorine, methyl, methoxy, CF₃ or CN, R₂ is hydrogen, chlorine, methyl, methoxy, CF₃ or CN, R₃ is hydrogen, chlorine, methyl, methoxy and R₄ is hydrogen, chlorine, methyl, methoxy or R₃ and R₄ together with the phenyl ring to which they are bonded form a heteroaryl ring, and A is hydrogen, chlorine, methyl, methoxy, CF₃, CN, unsubstituted or substituted phenyl or a radical of formula

wherein R₅ is hydrogen, chlorine, methyl, methoxy, nitro, CF₃ or CN and R₆ is hydrogen, chlorine, methyl, methoxy, nitro, CF₃ or CN, with the proviso that, when A is a radical of formula (2), R₃ and R₅ cannot be hydrogen and R₄ and R₆ cannot be methyl bonded in the 4-position.
 4. A process for the preparation of a diketopyrrolopyrrole pigment of formula (1) according to claim 2, which comprises first reacting a nitrile of formula

wherein R₁ is as defined above and X is a leaving group, with a compound of formula

wherein R₅ and R₆ are as defined above, and then reacting with a succinic acid diester, or oxidising a compound of formula

resulting from the compounds of formulae (50) and (51) to a compound of formula

or to a compound of formula

and then reacting with a succinic acid diester, or first reacting a mixture of two nitriles of formulae

wherein R₁ and R₂ are as defined above and X is a leaving group, with a compound of formula

wherein R₅ and R₆ are as defined above, and then reacting with a succinic acid diester, or oxidising a mixture of compounds of formulae

resulting from the compounds of formulae (50), (52) and (51) to a mixture of compounds of formulae

or to a mixture of compounds of formulae

and then reacting with a succinic acid diester to result in a suspension followed by discharging the suspension into a mixture comprising water, methanol and acetic acid at a temperature below 300° C., resulting in a pigment which has a particle size of less than or equal to 0.1 μm, has a transmission at 570-580 nm of less than 5% and a transmission at 615 nm of at least 80%.
 5. A high-molecular-weight polymeric material according to claim 1 comprising at least one diketopyrrolopyrrole pigment, which pigment has a particle size of less than or equal to 0.1 μm, has a transmission at 570-580 nm of less than 5% and a transmission at 615 nm of at least 80%, and consists of compounds of formula

wherein R₁ is hydrogen, chlorine, methyl, methoxy, CF₃ or CN, R₂ is hydrogen, chlorine, methyl, methoxy, CF₃ or CN, R₃ is hydrogen, chlorine, methyl, methoxy and R₄ is hydrogen, chlorine, methyl, methoxy or R₃ and R₄ together with the phenyl ring to which they are bonded form a heteroaryl ring, and A is hydrogen, chlorine, methyl, methoxy, CF₃, CN, unsubstituted or substituted phenyl or a radical of formula

wherein R₆ is hydrogen, chlorine, methyl, methoxy, nitro, CF₃ or CN and R₀ is hydrogen, chlorine, methyl, methoxy, nitro, CF₃ or CN.
 6. A high-molecular-weight polymeric material according to claim 5, wherein, in formula (1a), R₁ is hydrogen, chlorine or methyl, R₂ is hydrogen, chlorine or methyl, R₃ is hydrogen, chlorine or methyl, R₄ is hydrogen, chlorine or methyl and A is hydrogen, chlorine, methyl or phenyl.
 7. A high-molecular-weight polymeric material according to claim 5, wherein, in formula (1a), A is a radical of formula (2) in which R₅ is hydrogen, methyl or methoxy and R₆ is hydrogen, methyl or methoxy.
 8. A high-molecular-weight polymeric material according to claim 1, wherein the high-molecular-weight organic material is based on acrylates or methacrylates.
 9. A process for the production of colour filters, which process comprises applying a coating containing a diketopyrrolopyrrole pigment of formula (1) according to claim 1 to a transparent substrate or pigmenting a transparent substrate with said pigment.
 10. A process for the production of colour filters according to claim 9, wherein the coating or transparent substrate comprises a high-molecular-weight polymeric material based on acrylates or methacrylates.
 11. A colour filter comprising a diketopyrrolopyrrole pigment of formula (1) according to claim
 2. 12. A high-molecular-weight polymeric material according to claim 6, wherein, in formula (1a), A is a radical of formula (2) in which R₅ is hydrogen, methyl or methoxy and R6 is hydrogen, methyl or methoxy.
 13. A colour filter comprising a high-molecular-weight polymeric material according to claim
 1. 